Optical fiber connector

ABSTRACT

The present invention provides an optical fiber connector for making high-precision optical connections between optical fibers. During assembly, a ferrule is rotationally adjusted around its axis 360° without stepping. The assembly, including this rotational adjustment, can be performed easily and reliably.  
     An optical fiber connector  1  comprises: a housing  2  that can be mounted on and removed from an adapter A; a ferrule  3  through which a cladding portion F 1  at the end of an optical fiber F is inserted is rotatably housed in the housing  2  so that it can move along the axial direction; a compression coil spring  4  biasing the ferrule  3  in the axial end direction; and a rotation-restricting slide mechanism  5  that restricts rotation of the ferrule  3  relative to the housing  2  at the base-end side of the housing  3  and that allows the ferrule  3  to slide in the axial direction.

FIELD OF THE INVENTION

[0001] The present invention relates to an optical fiber connector witha housing, a ferrule, and a compression coil spring. More specifically,the present invention relates to an optical fiber connector with arotation-restricting slide mechanism that restricts the rotation of theferrule relative to the housing and that allows the ferrule to slidealong the axis.

BACKGROUND OF THE INVENTION

[0002] Conventionally, when making an optical connection between opticalfibers, an optical fiber connector (hereinafter referred to as aconnector) is attached to each of the ends of the two optical fibers.These two connectors are connected to an adapter so that the endsurfaces of the optical fibers abut and form a connection.

[0003] This type of connector generally comprises: a housing that isattachable to and removable from an adapter; a ferrule housed in thehousing that can move along an axial direction; and a compression coilspring mounted in the housing and biasing the ferrule along the axistoward the free leading end.

[0004] A fiber insertion hole (e.g., with a diameter of 127 microns) isformed at the axial center of the ferrule. Cladding portion (e.g., witha diameter of 125 microns) at the end of the optical fiber is insertedthrough and supported in the fiber insertion hole.

[0005] The ferrule and the end surface of the cladding portion in eachconnector are polished to form a co-planar surface. When the twoconnectors are connected via the adapter, the end surfaces of theferrules of the connectors are pressed by the compression coil spring sothat the end surfaces of the ferrules abut each other and form aconnection. As a result, the end surfaces of the cladding portion arepressed against each other in a stable manner to form a connection.

[0006] However, the fiber insertion hole of the ferrule is often formedeccentric relative to the axial center due to production tolerances andthe like (e.g., eccentricities of 1 micron or less). Thus, at theconnection surface of the optical fibers, there may be a radial offsetbetween the fiber insertion holes of the ferrules. In other words, therecan be a radial offset between the cladding portion (i.e., the core(e.g., 9 microns in diameter) formed at the center of the claddingportion) of the two optical fibers inserted into the fiber insertionholes. This leads to optical loss and a reduction in opticaltransmission rates.

[0007] The present applicant has implemented a connector with a ferruleprovided with a hexagonal flange and a hexagonal hole formed inside thehousing that can engage with a hexagonal flange. In this connector, whenthe ferrule is housed in the housing, the hexagonal flange engages withthe hexagonal hole while being biased by the compression coil spring.Thus, the ferrule cannot rotate relative to the housing.

[0008] In this connector, at an assembling and adjusting stage, once theferrule is housed in the housing, the engagement between the hexagonalflange and the hexagonal hole is released by inserting the tip of aspecialized jig from the end of the housing to apply pressure againstthe biasing force from the compression coil spring. Then, the jig isrotated to rotationally adjust the ferrule relative to the housing,thereby allowing the positioning at one of six positions at which thehexagonal flange and the hexagonal hole can engage. The position that isselected from the six positions is the position at which the radialoffset between the fiber insertion holes is minimized. When the tip ofthe jig is removed from the housing, the hexagonal flange re-engageswith the hexagonal hole so that the ferrule cannot rotate relative tothe housing.

[0009] Japanese Laid-Open Patent Publication Number 8-160255 discloses aconnector with a stop ring which is screwed to the inside of thehousing. A key on this stop ring slidably engages with a key grooveformed on a flange of a ferrule and extending along the axial direction.When assembling this connector, the ferrule and the stop ring can berotated 360° around the axis in a non-stepping manner relative to thehousing. Then, adhesive is injected into the housing so that the housingand the stop ring are secured and the ferrule cannot rotate relative tothe housing.

[0010] In polarization-retaining optical fibers, the cladding portion isformed with a core and a stress application section (e.g., a quartzglass with additives, which is formed from B₂O₃). Light is transmittedwhile a predetermined polarization state is retained. Thus, whenconnecting together polarization-retaining optical fibers, thepolarization-retaining optical fibers and their cladding portions mustbe connected to transmit light while the polarization state is retainedby adjusting the rotational phase.

[0011] In the connector implemented by the present applicant, thehexagonal flange of the ferrule is engaged with the hexagonal hole inthe housing. This prevents rotation of the ferrule relative to thehousing. However, the hexagonal flange and the hexagonal hole can engageonly at any one of six positions. As a result, it is difficult toeliminate completely optical loss at the connection surface between theoptical fibers, thereby reducing the optical transmission rate.

[0012] Also, in this connector, after the ferrule is housed in thehousing, the tip of a specialized jig is pushed in from the leading endof the housing to release the engagement of the hexagonal flange and thehexagonal hole. The jig is then rotated to adjust the angle of theferrule relative to the housing. Since the ferrule cannot be adjustedwhile observing from the leading end, making the adjustments for theappropriate positioning of the ferrule becomes more difficult.

[0013] In the connector of Japanese Laid-Open Patent Publication Number8-160255, the ferrule that can be rotationally adjusted 360° around itsaxis relative to the housing in a non-stepping manner. Thus, reductionin the optical transmission rate can be minimized. However, a stop ringis screwed to the inside of the housing, thereby making it not easy tomake rotational adjustments by rotating the ferrule and the stop ringrelative to the housing.

OBJECT AND SUMMARY OF THE INVENTION

[0014] The object of the present invention is to provide an opticalfiber connector for making high-precision optical connections betweenoptical fibers wherein a rotation-restricting slide mechanism isdisposed toward the base end of a housing. Thus, the ferrule can berotationally adjusted 360° in a non-stepping manner during assembly, andthe assembly of the connector, which includes the rotational adjustmentoperation, can be performed simply and reliably.

[0015] In the optical fiber connector according to the presentinvention, an optical fiber connector is attached to an end of anoptical fiber and used with an adapter in an optical connection. Theoptical fiber connector comprises: a housing that is attachable to andremovable from the adapter; a ferrule through which a cladding portionat the end of the optical fiber is inserted and supported and which ishoused slidably toward an axial direction in the housing in a rotatablemanner during assembly; a compression coil spring mounted in thehousing; and a rotation-restricting slide mechanism disposed toward abase end of the housing. The compression coil spring biases the ferruletoward the end along an axis, and the rotation-restricting slidemechanism restricts the rotation of the ferrule relative to the housingand allows the ferrule to slide along the axis.

[0016] The ferrule is housed in the housing so that it can move alongthe axis, and the compression coil spring mounted in the housing biasesthe ferrule toward the end. The cladding portion at the end of theoptical fiber is inserted through and is supported by the ferrule. Therotation-restricting slide mechanism positioned toward the base end ofthe housing restricts the rotation of the ferrule relative to thehousing and allows the ferrule to slide along the axis relative to thehousing.

[0017] During the assembly of the optical fiber connector, the ferruleis rotatably supported in the housing. Thus, the ferrule can berotationally adjusted relative to the housing so that, for example, therotational phase can be easily and reliably adjusted to maximize theoptical transmission rate for standard optical fibers. Forpolarization-retaining optical fibers, the rotational phase can beeasily and reliably adjusted to minimize polarization cross-talk. Aftermaking these adjustments, the rotation-restricting slide mechanism canrestrict rotation of the ferrule relative to the housing while allowingthe ferrule to slide along the axis.

[0018] When two optical fiber connectors are connected to the ends of anadapter, the compression coil spring presses together the end surfacesof the ferrules of the optical fiber connectors to form an opticalconnection. Thus, the end surfaces of the cladding portion of theoptical fibers are connected in a stable manner, allowing ahigh-precision optical connection between the optical fibers.

[0019] In order to provide high-precision optical connections betweenoptical fibers, the ferrule can be rotationally adjusted continuously360° around the axis during the assembly stage. The optical fiberconnector assembly operation, including this rotational adjustmentoperation, can be performed easily and reliably.

[0020] According to an embodiment of the present invention, the housingof the optical fiber connector can comprise: a main housing body that isattachable to and removable from the adapter; and an extender cap whichis engaged with and connected to a base end of the main housing body.When the main housing body, the ferrule, and the compression coil springare assembled, the ferrule and the compression coil spring are housed inthe main housing body while the main housing body is separated from theextender cap. Then, the extender cap can be easily engaged with andattached to the main housing body. At this stage, the ferrule can berotationally adjusted relative to the housing easily and reliably.

[0021] According to an embodiment of the present invention, the ferrulecan comprise a base-end screw inserted through the extender cap andprojecting toward the base end of the housing, and therotation-restricting slide mechanism can comprise a slit, a key member,an adjustment nut, and an adhesive section. The slit is formed on theextender cap and extends along the axis. The key member comprises a keywhich slidably engages with the slit and fits on the outside of thebase-end screw of the ferrule. Thus, the key is movable along the axialdirection relative to the housing, but the key cannot rotate relative tothe housing. The adjustment nut abuts a base-end surface opposite fromthe key of the key member, and the adjustment nut fits on the outside ofand is screwed to the base-end screw of the ferrule. The adhesivesection secures the adjustment nut and the key member.

[0022] Since the key of the key member slidably engages with the slit,which extends along the axis on the extender cap, the key member canslide along the axis relative to the housing while being prevented fromrotating. The adjustment nut abuts the base-end surface of the keymember, and the adjustment nut and the key member are secured by theadhesive section. Since the adjustment nut fits outside of and isscrewed onto the base-end screw of the ferrule, the ferrule is preventedfrom rotating relative to the housing while being able to slide alongthe axis.

[0023] The ferrule comprises the base-end screw, which is insertedthrough the extender cap and projects toward the base end of thehousing. The rotation-restricting slide mechanism is disposed near thebase-end screw, thereby allowing the ferrule to be observed from theleading end while the ferrule is rotationally adjusted. After thisadjustment operation, the key member, the adjustment nut, and the likecan be assembled easily to form the rotation-restricting slidemechanism.

[0024] According to an embodiment of the present invention, therotation-restricting slide mechanism can comprise an adhesive section,which secures the ferrule and the adjustment nut. Rotation of theferrule relative to the housing can be reliably restricted.

[0025] According to an embodiment of the present invention, the base-endscrew of the ferrule can comprise a rotation operation section forrotating the ferrule. The rotation operation section can be grasped witha rotation tool or the like, and the ferrule can be rotationallyadjusted easily.

[0026] According to an embodiment of the present invention, theadjustment nut and the key member can be secured by the adhesive sectionafter the ferrule has been rotationally adjusted relative to the housingand the key member so that the rotational phase maximizes an opticaltransmission rate. Thus, the assembly of the optical fiber connector,which includes the rotational adjustment of the ferrule, can beperformed easily and reliably to maximize the optical transmission rate.

[0027] According to an embodiment of the present invention, theadjustment nut and the key member are secured by the adhesive sectionafter the ferrule has been rotationally adjusted relative to the housingand the key member so that the rotational phase minimizes polarizationcross-talk. Thus, the assembly of the optical fiber connector, whichincludes the rotational adjustment of the ferrule, can be performedeasily and reliably to minimize polarization cross-talk.

[0028] According to another embodiment of the present invention, theferrule can include a base-end threaded section that passes through theextender cap and extends to the base end of the housing. Therotation-restricting slide mechanism can include a retention membersecurely disposed on the extender cap, an axially extended slit on theretention member, a nut serving as an adjustment nut, and a key formedintegrally on the adjustment nut. A ferrule is inserted through theretention member. The adjustment nut is movably housed in the retentionmember and fits onto the outside of the base-end threaded section of theferrule via threading. The adjustment nut is formed integrally with akey which is slidably engaged with the slit.

[0029] When the key of the adjustment nut is slidably engaged with theaxially oriented slit of the retention member, the adjustment nut canslide axially relative to the housing while being prevented fromrotating relative to the housing. Since the nut section of theadjustment nut fits via threading onto the base-end threaded section ofthe ferrule, the ferrule is prevented from rotating relative to thehousing while being allowed to slide axially.

[0030] When the nut section and the key are formed integrally in theadjustment nut, the rotation-restricting slide mechanism can have asimple structure. This provides advantages in production costs whilesimplifying the assembly of the optical fiber connector with arotation-restricting slide mechanism.

[0031] When the adjustment nut fits inside the retention member and isguided so that it can slide in the axial direction, the ferrule, whichis formed integrally with the adjustment nut, can move axially in asmooth manner. Also, the retention member formed from metallic materialis secured so that it fits inside the extender cap, and therefore, thestrength of the retention member can be increased and the adjustment nutcan be guided reliably.

[0032] When the rotation-restricting slide mechanism includes anadhesive section for securing the ferrule and the adjustment nut,rotation of the ferrule relative to the housing can be reliablyrestricted. When the rotation operation section for rotating the ferruleis formed at the base-end threaded section of the ferrule, a rotationtool or the like can engage with the rotation operation section, and therotation tool or the like can be used to easily rotate and adjust theferrule.

[0033] When the rotation-restricting slide mechanism includes the key,the adjustment nut and the key can be secured by the adhesion section sothat the ferrule is rotationally adjusted and set, relative to thehousing and the key, to a rotational phase that maximizes lighttransmission efficiency. This arrangement provides easy and reliableassembly of the optical fiber connector, which includes rotationallyadjusting the ferrule to maximize light transmission efficiency.Alternatively, the adjustment nut and the key can be secured by theadhesion section with the ferrule rotationally adjusted relative to thehousing and key member so that rotational phase minimizes polarizationcross-talk.

[0034] The above, and other objects, features, and advantages of thepresent invention will become apparent from the following descriptionread in conjunction with the accompanying drawings, in which likereference numerals designate the same elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035]FIG. 1 is an exploded side elevational view of an optical fiberconnector according to an embodiment of the present invention;

[0036]FIG. 2 is a side elevational view of an optical fiber connectorwith the cap and boot removed;

[0037]FIG. 3 is a side elevational view of an optical fiber connectorwith the cap and boot mounted;

[0038]FIG. 4 is a perspective view of an optical fiber connector;

[0039]FIG. 5 is a side elevational view with a partial cross section ofan optical fiber connector;

[0040]FIG. 6 is a side elevational view of an extender cap;

[0041]FIG. 7 is an elevational view of the extender cap of FIG. 6 asseen from arrow 7 of FIG. 6;

[0042]FIG. 8 is a cross-sectional view of a ferrule;

[0043]FIG. 9 is an elevational view of the ferrule of FIG. 8 as seenfrom arrow 9 of FIG. 8;

[0044]FIG. 10 is a plan view of a key member;

[0045]FIG. 11 is an elevational view of the key member of FIG. 10 asseen from arrow 11 of FIG. 10;

[0046]FIG. 12 is an elevational view of the key member of FIG. 10 asseen from arrow 12 of FIG. 10;

[0047]FIG. 13 is a side elevational view of an adjustment nut;

[0048]FIG. 14 is an elevational view of the adjustment nut of FIG. 13 asseen from arrow 14 of FIG. 13;

[0049]FIG. 15 is an elevational view of the adjustment nut of FIG. 13 asseen from arrow 15 of FIG. 13;

[0050]FIG. 16 is an elevational view of the adjustment nut of FIG. 13 asseen from arrow 16 of FIG. 13;

[0051]FIG. 17 is a side elevational view with a partial cross section ofan adapter and an optical fiber connector;

[0052]FIG. 18 is a process diagram for the assembly of an optical fiberconnector;

[0053]FIG. 19 is an exploded side elevational view of an optical fiberconnector according to another embodiment of the present invention;

[0054]FIG. 20 is a vertical cross-sectional view of an optical fiberconnector;

[0055]FIG. 21 is a side elevational view of an extender cap;

[0056]FIG. 22 is an elevational view of the extender cap of FIG. 21 asseen from arrow 22 of FIG. 21;

[0057]FIG. 23 is a side elevational view of a ferrule;

[0058]FIG. 24 is an elevational view of the ferrule of FIG. 23 as seenfrom arrow 24 of FIG. 23;

[0059]FIG. 25 is a plan view of an adjustment nut;

[0060]FIG. 26 is an elevational view of the adjustment nut of FIG. 25 asseen from arrow 26 of FIG. 25;

[0061]FIG. 27 is an elevational view of the adjustment nut of FIG. 25 asseen from arrow 27 of FIG. 25;

[0062]FIG. 28 is a side elevational view of a reinforcement ring;

[0063]FIG. 29 is an elevational view of the reinforcement ring of FIG.28 as seen from arrow 29 of FIG. 28;

[0064]FIG. 30 is an elevational view of the reinforcement ring of FIG.28 as seen from arrow 30 of FIG. 28;

[0065]FIG. 31 is a cross-sectional view taken along line 31-31 of FIG.28;

[0066]FIG. 32 is a process diagram for the assembly of an optical fiberconnector;

[0067]FIG. 33 is a side elevational view of a rotation adjustment tool;and

[0068]FIG. 34 is an elevational view of the rotation adjustment tool ofFIG. 33 as seen from arrow 34 of FIG. 33.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] The embodiments of the present invention will be described withreference to the accompanying drawings. In this embodiment, the presentinvention is implemented for an optical fiber connector attached to theleading end of an optical fiber to provide an optical connection betweenoptical fibers via an adapter. The up and down directions referenced inthe following description are shown in FIG. 1.

[0070] As shown in FIGS. 1-5, an optical fiber connector 1 (hereinafterreferred to as the connector 1) comprises: a housing 2 that can beattached to or removed from an adapter A (as shown in FIG. 17); aferrule 3 supporting a cladding portion F1 at the leading end of anoptical fiber F inserted through the ferrule 3 (as shown in FIG. 8)housed in the housing 2 so that it can move along the axis and so thatit can rotate during the assembly process; a compression coil spring 4mounted inside the housing 2 and biasing the ferrule 3 along the axistoward the leading end; and a rotation-restricting slide mechanism 5,disposed toward the base end of the housing 2, restricting the ferrule 3from rotating relative to the housing 2 and allowing the ferrule 3 toslide along the axis.

[0071] The housing 2 comprises a main housing body 10 that can beattached to or removed from the adapter A and that is formed from asynthetic resin; and an extender cap 15 formed from a synthetic resinand engaged with the base end of the main housing body 10.

[0072] The main housing body 10 comprises: a cylindrical section 11having a polygonal outer perimeter shape; and a lever 12 extendingdiagonally upward from the leading end of the cylindrical section 11 tothe base end. An inner collar 11 a is formed inside the cylindricalsection 11. A cylindrical insertion hole 11 b is formed at the leadingside of the inner collar 11 a. A pair of engagement holes 11 c areformed at the base-end section of the cylindrical section 11. The lever12 has appropriate elasticity along the up/down direction, and a pair ofengagement projections 12 a are formed on the lever 12.

[0073] As shown in FIGS. 6 and 7, an extender cap 15 comprises: acylindrical section 16; and a rotation restricting section 17 formedtoward the base end of the cylindrical section 16. A collar 16 a havingthe same outer perimeter shape as the cylindrical section 11 of the mainhousing body 10 is formed at the base end of the cylindrical section 16.A pair of engagement claws 16 b is formed on the outer perimeter surfaceof the leading end section of the cylindrical section 16. The rotationrestriction section 17 comprises a pair of semi-circular cylindricalsections 17 a. A taper is formed at a large-diameter section 17 b at thebase end of each semi-circular cylindrical section 17 a.

[0074] The cylindrical section 16 is pressed inside the cylindricalsection 11 of the main housing body 10. With the collar 16 a abuttingthe base-end surface of the cylindrical section 11, the pair ofengagement claws 16 b engage with the pair of engagement holes 11 c sothat the extender cap 15 engages with the main housing body 10. A pairof slits 29 in the rotation-restricting slide mechanism 5 are formedbetween the pair of semicircular cylindrical sections 17 a of therotation restricting section 17 of the extender cap 15.

[0075] As shown in FIGS. 8 and 9, the ferrule 3 comprises a main ferrulebody 20 (e.g., approximately 18 mm long) formed from a stainless steel;and a cylinder 27 formed from zirconia (e.g., with a 1.3 mm diameter anda length of approximately 5 mm).

[0076] A fiber insertion hole 21 (e.g., with a diameter of 1 mm) isformed on the main ferrule body 20, and a fitting hole 22 having alarger diameter than the fiber insertion hole 21 is formed at theleading end of the main ferrule body 20. The base-end section of thecylinder 27 fits and is secured inside the fitting hole 22. A fiberinsertion hole 28 (e.g., with a diameter of 127 microns) in the cylinder27 is continuous with the fiber insertion hole 21 in the main ferrulebody 20.

[0077] The surface covering at the leading end of the optical fiber F ispeeled away to expose the cladding portion F1. The cladding portion F1is inserted into the fiber insertion hole 28 of the cylinder 27. A coreF2, which includes the surface covering toward the base-end side of thecladding portion F1, is inserted into the fiber insertion hole 21 of themain ferrule body 20 so that the end of the core F2 abuts the cylinder27. Then, the cylinder 27 and the end surface of the cladding portion F1are polished to be co-planar.

[0078] With the ferrule 3 housed in the housing 2, the leading end ofthe cylinder 27 is projected forward slightly from the housing 2. Also,the main ferrule body 20 is inserted into the extender cap 15 so that itprojects toward the base-end side of the housing 2. A base-end screw 24is formed on the section of the main ferrule body 20 that projectstoward the base-end side of the housing 2.

[0079] A rotation operation section 25 used to rotate the ferrule 3 isformed by beveling the base-end screw 24. Since the flange 23 can beengaged with the inner collar 11 a when the ferrule 3 is housed in thehousing 2, the ferrule 3 cannot slip out from the leading end of thehousing 2.

[0080] As shown in FIGS. 1 and 5, the compression coil spring 4 fitsonto the main ferrule body 20 and is interposed between the extender cap15 and the flange 23 of the ferrule 3. Most of the compression coilspring 4 is housed in the cylinder 16 of the extender cap 15.

[0081] As shown in FIGS. 1, 2, and 5, the rotation-restricting slidemechanism 5 comprises: a pair of axially-oriented slits 29 formed on theextender cap 15; a metal key member 30 fitting onto the base-end screw24 of the ferrule 3 and formed with a pair of keys 31 slidably engagingwith the slits 29; a metal adjustment nut 35 abutting the base-endsurface opposite from the keys 31 of the key member 30 and fitting ontothe base-end screw 24 of the ferrule 3; a first adhesive section 39 asecuring the adjustment nut 35 and the key member 30; and a secondadhesive section 39 b securing the ferrule 3 and the adjustment nut 35.

[0082] The pair of slits 29 are formed at axially-symmetrical opposingpositions. As shown in FIGS. 10-12, the key member 30 comprises a pairof keys 31 and a ring 32. The pair of keys 31 are formed at axiallysymmetrical positions and are extended from the ring 32 along the axistoward the end. An insertion hole 32 a is formed in the ring 32, and aninsertion hole 32 b having a larger diameter than the insertion hole 32a is formed at the base-end side of the insertion hole 32 a.

[0083] As shown in FIGS. 13-16, the adjustment nut 35 comprises a mainnut body 36 with flat portions 38 and a small-diameter nut section 37having a smaller diameter than the main nut body 36. The small-diameternut section 37 is positioned toward the leading end of the main nut body36. A threaded groove 35 a is formed on the inner perimeter sections ofthe main nut body 36 and the small-diameter nut section 37. Thesmall-diameter nut section 37 is inserted into the insertion hole 32 bin the ring 32 of the key member 30, and a shelf 36 a at the leading endof the main nut body 36 abuts the base-end surface of the ring 32 of thekey member 30.

[0084] The first adhesive section 39 a is formed by hardened adhesiveapplied between the key member 30 and the adjustment nut 35. The secondadhesive section 39 b is formed by hardened adhesive applied between theferrule 3 and the adjustment nut 35.

[0085] As shown in FIGS. 1-4 and the like, if the connector 1 is notconnected to the adapter A, a cap 6 covering the cladding portion F1 andthe like can be inserted in the cylindrical insertion hole 11 b of thehousing 2. Also, a rubber boot 7 covering the rotation restricting slidemechanism 5 is mounted so that the boot 7 engages with the rotationrestricting section 17.

[0086] As shown in FIG. 17, the adapter A is formed by connecting a pairof opposing split adapter members 40. Each of the split adapter members40 comprises: a housing storage section 41; a cylindrical section 42formed at the far surface from the housing storage section 41; and apair of slide sections 43 formed above the housing storage section 41.

[0087] To connect the connector 1 to the adapter A, the housing 2 isinserted into the housing storage section 41. When the housing 2 iscompletely housed in the housing storage section 41, the cylindricalsection 42 is inserted into the cylinder insertion hole 11 b of thehousing 2 and the cylinder 27 of the ferrule 3 is inserted into thecylindrical section 42.

[0088] When the housing 2 is inserted into the housing storage section41, the pair of engagement projections 12 a on the lever 12 are pusheddownward by the pair of slide sections 43. More specifically, the lever12 is elastically deformed downward and when the housing 2 is completelyhoused in the housing storage section 41, the lever 12 is restored sothat the pair of engagement projections 12 a engages with the pair ofslide sections 43 to prevent slippage of the connector 1.

[0089] When two connectors 1 are connected to both ends of the adapterA, the end surfaces of the ferrules 3 are pushed together by thecompression coil spring 4. Thus, the end surfaces of the two claddingportions F1 abut each other and are connected, and this connection ismaintained in a stable manner. When separating the connectors 1 from theadapter A, the lever 12 is pushed downward to release the engagement ofthe engagement projections 12 a and the slide sections 43, therebyallowing the connector 1 to be slipped out from the adapter A.

[0090] Next, a method for assembling the connector 1 will be described.

[0091] It is assumed that the main housing body 10, the extender cap 15,the ferrule 3, the compression coil spring 4, the key member 30, theadjustment nut 35, and the like are produced using predetermined, widelyknown methods before the connector 1 is assembled. The steps forassembling the connector 1 are indicated by Pi (i=1, 2, 3, . . . ).

[0092] As shown in FIG. 18, at step P1, the main housing body 10, theextender cap 15, the ferrule 3, and the compression coil spring 4 areassembled. At this step, the ferrule 3 is housed in the housing 2 sothat it can be rotated relative to the housing 2. Next, at step P2, thekey member 30 fits onto the base-end screw 24 of the ferrule 3, and thekeys 31 are engaged with the slits 29 of the extender cap 15.

[0093] Next, at step P3, adhesive is applied to the base-end surface ofthe key member 30 and its vicinity. At step P4, the adjustment nut 35 isfit onto the base-end screw 24 of the ferrule 3 before the adhesivesets. When assembling this adjustment nut 35, the flange 23 of theferrule 3 is biased toward the leading end and engages with the innercollar 11 a of the housing 2. The adjustment nut 35 is abutted againstthe key member 30 so that the there is maximum engagement between theslit 29 and the key 31.

[0094] Also, before the adhesive applied at step P3 sets, the ferrule 3is rotated for adjustment at step P5. The rotation operation section 25is supported and rotated using a rotating tool or the like while theoptical transmission rate is measured from the leading end of theferrule 3 using an optical characteristic measuring tool. The ferrule 3is positioned so that optical loss is minimized.

[0095] Next, at step P6, adhesive is applied between the adjustment nut35 and the base-end screw 24 of the ferrule 3. Finally, while theferrule 3 and the adjustment nut 35 are fixed in position at step P7,the adhesive applied at steps P3 and P6 is set in order to form thefirst and the second adhesive sections 39 a, 39 b, thereby completingthe assembly process and producing the connector 1.

[0096] With this connector 1, the rotation restricting slide mechanism 5prevents the ferrule 3 positioned toward the base end of the housing 2from rotating relative to the housing 2 and also allows the ferrule 3 toslide along the axis. As a result, while the connector 1 is assembled,the ferrule 3 can be rotated 360° around the axis in a non-steppingmanner in order to provide a high-precision optical connection betweenthe optical fibers F.

[0097] The housing 2 comprises the main housing body 10, which isattachable to and removable from the adapter A, and an extender cap 15,which engages and connects to the base end of the main housing body 10.When the housing 2, the ferrule 3, and the compression coil spring 4 areassembled, the ferrule 3 and the compression coil spring 4 are stored inthe main housing body 10 while the main housing body 10 and the extendedcap 15 are separated. Then, the extender cap 15 is engaged with andconnected to the main housing body 10, thereby allowing easy assemblyand allowing the simple and reliable rotational adjustment of theferrule 3 relative to the housing 2.

[0098] The ferrule 3 comprises the base-end screw 24, which is insertedthrough the extender cap 15 and projects from the base-end side of thehousing 2. The rotation-restricting slide mechanism 5 comprises theslits 29 formed on the extender cap 15, the key member 30, theadjustment nut 35, and the first and second adhesive sections 29 a, 29b. This rotation-restricting slide mechanism 5 reliably restricts therotation of the ferrule 3 relative to the housing 2 while allowingreliable sliding motion along the axis.

[0099] The rotation operation section 25 is formed on the base-end screw24 of the ferrule 3 so that the rotation operation section 25 can beheld with a rotating tool and the ferrule 3 can be easily rotated foradjustment relative to the housing 2 while observing the end of theferrule 3. After adjustments are made, the key member 30, the adjustmentnut 35, and the like can be assembled to easily form therotation-restricting slide mechanism 5.

[0100] In addition to the first adhesive section 39 a, which secures theadjustment nut 35 and the key member 30, the rotation-restricting slidemechanism 5 comprises the second adhesive section 39 b, which securesthe ferrule 3 and the adjustment nut 35. Thus, the ferrule 3 is reliablyprevented from rotating relative to the housing 2.

[0101] Thus, in order to provide an optical connection between theoptical fibers F that has a high degree of precision, arotation-restricting slide mechanism 5 is disposed toward the base endof the housing 2, and the ferrule 3 can be rotationally adjusted bydesired degree less than 360° in a non-stepping manner around the axis.Thus, the rotational phase can be adjusted to provide maximum opticaltransmission, while the assembly process, including the rotationaladjustment, can be simple and reliable.

[0102] While not shown in the figures, polarization-retaining fiberscomprise cladding portion, a core, and a stress application section(e.g., a quartz glass with additives; formed from B₂O₃). Light istransmitted while retaining a predetermined polarization. Thus, whenconnecting these polarization-retaining optical fibers, thesepolarization-retaining optical fibers must be adjusted for predeterminedrotational phases (i.e., rotational phases that minimize polarizationcross-talk) so that light can be transmitted while polarization ismaintained.

[0103] In this case, for example, the cladding portion of thepolarization-retaining optical fiber can be connected to the connector 1so that it is prevented from rotating. When assembling this connector 1,the ferrule 3 can be rotationally adjusted around the axis to provide apredetermined rotational phase for the polarization-retaining opticalfiber. As a result, polarization-retaining optical fibers can beconnected so that light is transmitted with the predeterminedpolarization reliably maintained. Compared to conventional technologiesthat use a jig to rotationally adjust the ferrule from the leading freeend, the present invention allows the ferrule 3 to be rotationallyadjusted from the base end. Thus, when the connector is used forpolarization-retaining optical fibers, rotational adjustments can bemade in a non-stepping manner while observing the leading free endsurface of the ferrule 3.

[0104] Other modifications may be effected without departing from thespirit of the present invention, and the present invention can beimplemented for different types of optical fiber connectors.

[0105] Next, an optical fiber connector according to another embodimentof the present invention will be described. Since the adapter A and theoptical fiber F are identical to those from the embodiment describedabove, like numerals will be used and the corresponding descriptionswill be omitted. Also, the up and down directions indicated in FIG. 19will be used as references in the description.

[0106] As shown in FIGS. 19-31, the optical fiber connector 1A(hereinafter referred to as the connector 1A) comprises a housing 2A, aferrule 3A, a compression coil spring 4A, a rotation-restricting slidemechanism 5A, and the like. The housing 2A is attachable to andremovable from the adapter A. A cladding portion F1 at the end of theoptical fiber F is inserted through the ferrule 3A. The ferrule 3Aprovides support and is housed in the housing 2A so that the ferrule 3Acan move axially and can rotate during the assembly process. Thecompression coil spring 4A is mounted in the housing 2A and biases theferrule 3A toward the leading end in the axial direction of the housing2A. The rotation-restricting slide mechanism 5A restricts the rotationof the ferrule 3A relative to the housing 2A at the base-end side of thehousing 2A and allows the ferrule 3A to slide along the axial direction.

[0107] As shown in FIGS. 19 and 20, the housing 2A comprises a mainhousing body 50 and a synthetic resin extender cap 55. The main housingbody 50 is formed from a synthetic resin and is attachable to anddetachable from the adapter A. The synthetic resin extender cap 55 canengage with and be joined to the base end of the main housing body 50.

[0108] The main housing body 50 has a structure similar to that of themain housing body 10 of the embodiment described above and comprises acylindrical section 51 and a lever section 52. The cylindrical section51 comprises an inner collar 51 a, a cylindrical insertion opening 51 b,and a pair of engagement holes 51 c. A pair of engagement projections 52a are formed on the lever section 52 of the main housing body 50.

[0109] As shown in FIGS. 21 and 22, the extender cap 55 comprises afirst cylindrical section 56 with a polygonal outer shape, a secondcylindrical section 57 also with a polygonal outer shape, and a leversection 58. The second cylindrical section 57 is disposed at the baseend of the first cylindrical section 56. The lever section 58 extendsupward and diagonally from an upper section of the second cylindricalsection 57 from the base end to the leading end. A retention member 70of the rotation-restricting slide mechanism 5A fits inside and issecured to the extender cap 55.

[0110] The retention member 70 is formed from a metallic material. Thelength of the retention member 70 is approximately twice the length ofthe second cylindrical section 57 of the extender cap 55. The secondcylindrical section 57 of the extender cap 55 fits and is secured ontothe leading half of the retention member 70. The base-end half of theretention member 70 projects from the base end of the extender cap 55.

[0111] A pair of engagement claws 56 a are located on the outerperimeter surface of the first cylindrical section 56 of the extendercap 55. The outer diameter of the base end of the second cylindricalsection 57 is larger than the outer diameter of the first cylindricalsection 56. A shelf 57 a is located at the boundary between the firstcylindrical section 56 and the second cylindrical section 57.

[0112] The first cylindrical section 56 of the extender cap 55 fitstightly inside the cylindrical section 51 of the main housing body 50.The pair of engagement claws 56 a engage with the pair of engagementopenings 51 c while the shelf 57 a abuts the base-end surface of thecylindrical section 51. Thus, the extender cap 55 engages and connectsto the main housing body 50.

[0113] As shown in FIGS. 23 and 24, the ferrule 3A comprises a stainlesssteel main ferrule body 60 and a cylindrical body 67 formed fromzirconia, thereby essentially having the same structure as the ferrule 3from the embodiment described above.

[0114] More specifically, the main ferrule body 60 comprises a fiberinsertion opening 61, a fitting hole 62, a flange 63, and a base-endthreaded section 64. The base-end threaded section 64 is insertedthrough the extender cap 55 and extends toward the base end of thehousing 2A. The base-end section of the cylindrical body 67 fits intothe fitting hole 62 securely. The cylindrical body 67 is formed with afiber insertion opening 68.

[0115] A rotation operation section 65 is located on the base-endthreaded section 64 and allows the ferrule 3 to rotate. The rotationoperation section 65 comprises a pair of axially oriented slitspositioned symmetrical relative to the axis on the base-end threadedsection 64.

[0116] As shown in FIGS. 19 and 20, the compression coil spring 4A fitsonto the main ferrule body 60 of the ferrule 3A and is interposedbetween the flange 63 and the retention member 70. The leading end ofthe retention member 70 is positioned near the boundary between thefirst cylindrical section 56 and the second cylindrical section 57 ofthe extender cap 55. A section of the compression coil spring 4A ishoused in the first cylindrical section 56.

[0117] As shown in FIGS. 19 and 20, the rotation-restricting slidemechanism SA comprises the metal retention member 70, a pair of axialslits 71 on the retention member 70; a metal adjustment nut 75; and anadhesive section 79. The ferrule 3A is inserted through the retentionmember 70, which is securely disposed on the extender cap 55. The metaladjustment nut 75 movably housed in the retention member 70, and theadhesive section 79 secures the adjustment nut 74 to the ferrule 3A.

[0118] The pair of slits 71 are formed on the retention member 70 ataxially symmetrical positions and extend from the extender cap 55 to thebase-end half of the retention member 70 which projects toward the baseend.

[0119] As shown in FIGS. 25-27, the adjustment nut 75 comprises a nutsection 76 and a pair of keys 77 formed integrally with each other. Thenut section 76 fits onto the base-end threaded section 64 of the ferrule3A. The pair of keys 77 slidably engages with the pair of slits 71 ofthe retention member 70. The nut section 76 is inserted in the retentionmember 70 and is guided so that it can move along the axial direction.The pair of keys 77 are formed at axially symmetrical positions on thebase-end side of the nut section 76 and project radially outward fromthe nut section 76.

[0120] The adhesive section 79 is formed by setting an adhesive which isapplied between the adjustment nut 75 and the base-end threaded section64 of the ferrule 3A.

[0121] As shown in FIGS. 19 and 20, the connector 1A further comprises aboot 88, an attachment sleeve 85, and a reinforcement ring 80 secured tothe base-end side of the retention member 70.

[0122] As shown in FIGS. 19, 20, and 28-31, the reinforcement ring 80 isformed from a metallic material and comprises a cylinder 81, a pair ofclaws 82, and a collar 83. The pair of claws 82 are disposed at theleading end of the cylinder 81 and are positioned symmetrically to eachother relative to the axis. The collar 83 is disposed at the base end ofthe cylinder 81. The cylinder 81 is pushed into the base end of theretention member 70 and the pair of claws 82 engages with the pair ofslits 71 so that the collar 83 abuts against and is secured by thebase-end surface of the retention member 70.

[0123] As shown in FIGS. 19 and 20, the attachment sleeve 85 is formedfrom a metallic material and comprises a large-diameter cylinder section86 and a small-diameter cylinder section 87. The large-diameter cylindersection 86 is secured by being fitted and locked onto the outside of thebase-end section of the retention member 70. When the attachment sleeve85 is secured by being fitted and locked to the outside of the retentionmember 70, the reinforcement ring 80 provides reinforcement so that theretention member 70 is not crushed. The end of the boot 88 fits and issecured onto the outside of the large-diameter cylinder section 86 ofthe attachment sleeve 85. The boot 88 covers the attachment sleeve 85and the base-end half of the retention member 70 which projects from theextender cap 55 to the base-end side of the connector 1A.

[0124] Next, a method for making the connector 1A will be described.

[0125] The main housing body 50, the extender cap 55, the ferrule 3A,the compression coil spring 4A, the adjustment nut 75, the reinforcementring 80, the attachment sleeve 85, and the like are made usingpredetermined, well-known methods. These elements are made before theconnector 1A is assembled. The assembly of the connector 1A will bedescribed using the process diagram shown in FIG. 32 in which PiA (i=1,2, 3, . . . ) indicates the individual steps.

[0126] As shown in FIG. 32, the extender cap 55, the ferrule 3A, thecompression coil spring 4A, and the adjustment nut 75 are assembled instep P1A. The adjustment nut 75 is assembled by engaging the pair ofkeys 77 of the adjustment nut 75 with the pair of slits 71 of theretention member 70. Then, the compression coil spring 4A fits onto theoutside of the ferrule 3A, and the ferrule 3A is inserted through theextender cap 55 and the retention member 70. The ferrule 3A is rotatedso that it is inserted through the extender cap 55 and the retentionmember 70, and the base-end threaded section 64 engages and fits insidethe adjustment nut 80.

[0127] Next, at step P2A, the reinforcement ring 80 is assembled byengaging the pair of claws 82 of the reinforcement ring 80 with the pairof slits 71 of the retention member 70.

[0128] Next, at step P3A, the main housing body 50 and the extender cap55 are assembled. After the main housing body 50 and the extender cap 55are assembled, the flange 63 of the ferrule 3A, which is biased towardthe leading end by the compression coil spring 4A, engages with theinner collar 51 a of the housing 2A. At any one of steps P1A-P4A, theferrule 3A is rotated to adjust the engagement position of the ferrule3A with the adjustment nut 75 so that there is maximum engagementbetween the pair of keys 77 of the adjustment nut 75 and the pair ofslits 71 of the retention member 70.

[0129] Next, at step P4A, the ferrule 3A is rotationally adjusted. Arotation adjustment tool 90 used in this step, as shown in FIGS. 33 and34, comprises a hexagonal grip 91, an insertion opening 92 on the grip91, and a pair of forked insertion engagement sections 93 projectingfrom the grip 91 toward the leading end. An optical fiber F is attachedto the assembled ferrule 3A before the connector assembly process, andthe optical fiber F, extending through the retention member 70, extendstoward the base-end side of the retention member 70.

[0130] When the ferrule 3A is to be rotationally adjusted, the opticalfiber F, which extends toward the base-end side of the retention member70, is inserted through the insertion opening 92 of the rotationaladjustment tool 90. The pair of insertion engagement sections 93 areinserted from the base-end side of the retention member 70. The ends ofthe pair of insertion engagement sections 93 engage with the rotationoperation section 65 of the ferrule 3A. Then, the ferrule 3A is rotatedby turning the rotational adjustment tool 90 while the lighttransmission efficiency is measured using an optical characteristicsmeasuring device at the end of the ferrule 3A. The ferrule 3A is alignedto the position where optical loss is minimized.

[0131] Next, in step P5A, when the rotation adjustment tool 90 is pulledout, an injecting member, e.g., an injection needle for injection ofadhesive, is inserted into the base end of the retention member 70. Anadhesive is injected and applied to the section of the adjustment nut 75at the base end where it contacts the ferrule 3A. At step P6A, theferrule 3A is kept stationary while the adhesive applied at step P5Asets, thereby forming an adhesive section 79. Then, in step P7A, theattachment sleeve 85 and the boot 88 are assembled. The assembly of theconnector 1A is completed when the assembly of the attachment sleeve 85and the boot 88 is completed.

[0132] This connector 1A provides essentially the same operation andadvantages as the connector 1 of the embodiment described above.However, since the functions of the key member 30 and the adjustment nut35 are both provided by the adjustment nut 75, in which the nut section76 and the key 77 are formed integrally, the structure of therotation-restricting slide mechanism 5A can be simplified. This providesan advantage in production cost and also simplifies the assembly of theconnector 1A that includes this rotation-restricting slide mechanism 5A.

[0133] Also, since the adjustment nut 75 fits inside the retentionmember 70 and is guided so that it can move along the axis, the ferrule3A that is formed integrally with the adjustment nut 75 can be movedsmoothly along the axis.

[0134] Since the retention member 70 is metallic and fits inside and issecured to the extender cap 55, a pair of slits 71 can be reliablymachined in the retention member 70. Furthermore, the strength of theretention member 70 can be increased, and the adjustment nut 75 can bereliably guided. Also, the attachment sleeve 85 can fit onto the outsideof the retention member 70 and locked securely without deformation byreinforcing the retention member 70 with the reinforcement ring 80.

[0135] It is not required that the retention member 70 be formedseparately from the extender cap 55. The extender cap 55 and theretention member 70 can, for example, be formed integrally from asynthetic resin material.

[0136] In the embodiments described above, the connectors 1, 1Aoptically connect optical fibers to each other using an adapter.However, the connectors 1, 1A can also be used as connectors that formoptical connections using receptacles.

[0137] Various changes and modifications may be effected withoutdeparting from the spirit of the present invention, and the presentinvention can be implemented for different types of optical connectors.

[0138] Having described preferred embodiments of the invention withreference to the accompanying drawings, it is to be understood that theinvention is not limited to those precise embodiments, and that variouschanges and modifications may be effected therein by one skilled in theart without departing from the scope or spirit of the invention asdefined in the appended claims.

What is claimed is:
 1. An optical fiber connector attached to an end of an optical fiber and used with an adapter in an optical connection, said optical fiber connector comprising: a housing attachable to and removable from said adapter; a ferrule through which a cladding portion at said end of said optical fiber is inserted and supported, said ferrule being housed slidably toward an axial direction in said housing in a rotatable manner in an assembly step; a compression coil spring mounted in said housing and biasing said ferrule along an axis and toward said end of said optical fiber; and a rotation-restricting slide mechanism disposed toward a base end of said housing, said rotation-restricting slide mechanism restricting rotation of said ferrule relative to said housing and allowing a sliding motion along said axis.
 2. An optical fiber connector as described in claim 1 wherein: said housing comprises: a main housing body that is attachable to and removable from said adapter, and an extender cap engaged with and connected to said base end of said main housing body.
 3. An optical fiber connector as described in claim 2 wherein: said ferrule comprises a base-end screw inserted through said extender cap and projecting toward said base end of said housing; and said rotation-restricting slide mechanism comprises: a slit formed on said extender cap and extending along said axis; a key member comprising a key slidably engaging with said slit and fitting onto said base-end screw of said ferrule; an adjustment nut abutting a base-end surface opposite from said key of said key member and fitting onto and screwed to said base-end screw of said ferrule; and an adhesive section securing said adjustment nut and said key member.
 4. An optical fiber connector as described in claim 2 wherein: said ferrule comprises a base-end threaded section passing through said extender cap and extending to said base-end side of said housing; and said rotation-restricting slide mechanism comprises: a retention member fixed to said extender cap and through which said ferrule is inserted; an axially oriented slit formed on said retention member; an adjustment nut movably housed in said retention member and integrally formed from a nut section screwed to the outside of said base-end threaded section of said ferrule; and a key slidably engaged with said slit.
 5. An optical fiber connector as described in claim 4 wherein said adjustment nut fits inside said retention member and is guided to move in said axial direction.
 6. An optical fiber connector as described in claim 4 wherein said retention member is formed from a metal material and fits inside and is secured to said extender cap.
 7. An optical fiber connector as described in claim 3 wherein said rotation-restricting slide mechanism comprises an adhesion section for securing said ferrule and said adjustment nut.
 8. An optical fiber connector as described in claim 7 wherein a rotation operation section for rotating said ferrule is formed at said base-end threaded section of said ferrule.
 9. An optical fiber connector as described in claim 3 wherein: said ferrule is rotationally adjusted relative to said housing and said key member; and said adjustment nut and said key member are fixed by said adhesive section when a rotational phase is set to maximize light transmission efficiency.
 10. An optical fiber connector as described in claim 3 wherein: said ferrule is rotationally adjusted relative to said housing and said key member; and said adjustment nut and said key member are fixed by said adhesive section when a rotational phase is set to minimize polarization crosstalk.
 11. An optical fiber connector as described in claim 5 wherein said retention member is formed from a metal material and fits inside and is secured to said extender cap.
 12. An optical fiber connector as described in claim 4 wherein said rotation-restricting slide mechanism comprises an adhesion section for securing said ferrule and said adjustment nut.
 13. An optical fiber connector as described in claim 5 wherein said rotation-restricting slide mechanism comprises an adhesion section for securing said ferrule and said adjustment nut.
 14. An optical fiber connector as described in claim 6 wherein said rotation-restricting slide mechanism comprises an adhesion section for securing said ferrule and said adjustment nut.
 15. An optical fiber connector as described in claim 11 wherein said rotation-restricting slide mechanism comprises an adhesion section for securing said ferrule and said adjustment nut.
 16. An optical fiber connector as described in claim 12 wherein a rotation operation section for rotating said ferrule is formed at said base-end threaded section of said ferrule.
 17. An optical fiber connector as described in claim 13 wherein a rotation operation section for rotating said ferrule is formed at said base-end threaded section of said ferrule.
 18. An optical fiber connector as described in claim 14 wherein a rotation operation section for rotating said ferrule is formed at said base-end threaded section of said ferrule.
 19. An optical fiber connector as described in claim 15 wherein a rotation operation section for rotating said ferrule is formed at said base-end threaded section of said ferrule. 